Friday, June 27, 2014

Species That Don't Get Enough Publicity #7: Heterodontosaurus

Today’s animal we’re looking at you’ve probably heard of, or
perhaps not. Most dinosaur encylopedias and other comprehensive works mention
it, but it’s not in any museums outside its home, and it hasn’t made a single appearance
on big or TV screens. No toys, no
dedicated books, only a small bit of art for it. It seems that while the large
weird dinosaurs attract a great deal of attention, the smaller ones, even more
bizarre, do not. There’s a whole plethora of small but striking animals, but
we’re looking at one in particular from an obscure location that is absolutely
unique.

Perhaps besides its size (only 3 feet, the size of a small
dog) and its location (South
Africa), its very name makes it so obscure.
While Triceratops, Apatosaurus, and Tyrannosaurus are 4-5 syllable
monstrosities, Heterodontosaurus has a whopping 7 syllables and 18 letters, not
counting the rather small and bland species name tucki.The name, however, says a great deal on why
this dinosaur is so significant. It is in Greek, of course, meaning roughly
“Lizard with different types of teeth”

Teeth are the key here. There are two conditions in all
animals with teeth-heterodonty and homodonty. Extant reptiles, amphibians, and fish
have homodont dentition, meaning their teeth are identical in every way but in
stages of growth. A mature tooth of a snake, crocodile, or salamander will look
the same no matter where in the mouth it is. Most extant reptiles are diapsids,
meaning they also have two pairs of holes in their skulls above and behind the
eye sockets. All diapsids are homodonts, including dinosaurs. All dinosaurs
have one type of tooth; check this out next time you’re at a museum.

In contrast, almost synapsids (only one pair of holes behind
the eyes and ears) are heterodonts. Remember Dimetrodon? It gets its name from
the two different kinds of teeth-large, long incisors for cutting off chucks of
meat, and shorter, broader carnassials for chopping the meat into small
pieces.More advanced synapsids grew
canines for killing or fighting, and we retain these canines despite the fact
that they have lost their specialized function.

Heterodontosaurus is a dinosaur with three kinds of
teeth.In front of the skull, there is a
beak like later dinosaurs, but on the maxilla (upper jaw) of the beak there are
some small shearing teeth. Then we have tusks. This dinosaur had tusks: one
pair of long teeth, like that of a pig, on the lower mandible behind the beak

When A.J. Charig and A.W. Crompton discovered the skull in
1962, the tusks were the feature that stood out, of course. Since then,
numerous suggestions have made on how they were used. The beak, along with the
shape of the skull, places this animal at the base of the Ornithiscia,
plant-eaters that include Hadrosaurs, Ceratopsians, Stegosaurs and
ankylosaurus. Most herbivores with tusks or large canines like elephants,
hippopotamus, musk deer, muntjac deer, gibbons, monkeys, pigs and gorillas use
them for social purposes: they are used in duels between males for social
standing and mating rights. As well, they are deadly weapons used to inflict
horrific slashing wounds on predators with vicious bites.

Pandas and gorillas also use their large canines for tearing
open plant stemsor wood, and elephants
use their tusks to uproot trees, bringing down branches, and digging for water
and roots. No doubt Heterodontosaurus used its tusks in a variety of ways.

Finally, the cheek teeth indicate this animal was already a
specialized browser. The teeth are shaped in compact batteries, an adaptation
found in animals that chew their food. So while the sauropods and their
ancestors had to use their giant guts and gizzards filled with powerful
muscles, acid, and pebbles, ornithiscians were inventing chewing.

In 1976, a complete specimen was found, revealing another
unique anatomical trait. While it had three long fingers on each hand like most
dinosaurs, fingers tipped with long curved claws probably used for browsing,
digging, and fighting, it also had two small, vestigial fingers right next to
them.These tiny fingers, according to
their articulation, were opposable, much like the opposable pseudo-thumb of a
panda. So while the clawed fingers pulled branches towards the mouth, the smaller
fingers could grip them and articulate them.

The body is small and slender, something that would lend to
swift, nimble movement.It probably then
lived like the aforementioned musk deer and pigs. Like pigs, it might even have
been omnivorous, using the canines to grip meat or tear open termite mounds. As
in a previous article, strict herbivory is rare.

There’s one final twist to this animal; relatives of
Heterodontosaurus have been found in the same region and period-the more
primitive Abrictosaurus, distant relative Lesothosaurus, and the obscure sister
species Lychorhinus (attempts to synonymize it with Heterodontosaurus have
never been conclusive), and smaller Pegomastax, but they’re poorly definedand represented. Other relatives include Echinodon
from Britain and Fruitadens
from USA,
but it’s the Chinese Tianyulong that has been the best preserved and provided
another revelation.

Tianyulong was found to have been covered in filaments,
long, hollow, quill-like scales, something like the earliest feathers.This had led to the suggestion that all
dinosaurs had integument of some kind, be it fuzz or feathers. I think this is
a bit of a leap in logic and that it’s unsupported by evidence. After all, the
animal had canines, something that would imply all later dinosaurs had them as
well, which is false.

However, it’s likely that other members of the
Heterodontosaur family had these quills, and so Heterodontosaurus and all its
kin would be absolutely-bizarre looking. Imagine, if you will, the Upper Elliot
Formation, South Africa,
in the Sinemurian stage of the early Jurassic.The land is covered with vegetation; food for huge prosauropodmorphs:
Massospondylus, Aardonyx, Plateosauravus, Gryponyx, tiny Igavusaurus,giant Melanorosaurus. Predators would follow
the herds, picking off the juveniles and smaller prosauropods: the small
Megapnosaurus and the much, much larger Dracovenator.Megapnosaurus would also hunt the small
animals of the underbrush-the first mammals, lizards, insects, and small dinosaurs.
These small dinosaurs would run like deer, but with the quills of a porcupine,
the claws of anteaters and the teeth of boars; even if Megapnosaurus was small
and young enough to catch them, they would be in for a horrible fight with
their teeth and claws match by their prey’s.

In that land, ancestors of the great Triceratops and
Anatosaurus would live in the shadow of the sauropodmorphs; but overshadow them
in terms of their appearance-tiny, fuzzy, clawed, thumbed, and tusked.No other dinosaur can claim to have that, no
matter what their size. And that is what makes Heterodontosaurus so special.

So anyway, Hollywood, give this guy
a break. Museums, put him on display. Toy companies, here’s a new fresh face.
Authors, think about the crap you’re writing and how this genus could perk up
the place. And remember, shop Heterodontosaurus where you work or play. Or at
least learn how to pronounce the name.

About Me

Hi everyone! You may know me already, but 99% of you won't. I've decided to make a blog for myself. I'm a anthropology student who has returned to his original passion for palaeontology. Ever since I was little, I've been fascinated with the weird and wonderful animals that have inhabited our planet and I've made this blog to keep this in my mind and hopefully in yours. Most people blog about their interests, and while I've got a range of interests-see history and anthropology above, not to mention zoology, astronomy, art, cooking, science fiction and fantasy films and literature, and a myriad of others, the one I want to do for a living is the study of Earth's ancient past.

On this blog I'll review papers, talk about fossils, museums, and taxa, review art, film, literature, and our culture's view of paleontology, and share memories and insights. I've been inspired by the far better blogs of professional palaeontologists, and I'll share them as time goes on. I'm also open to requests and questions of opinions, the latest palaeo news, and discussions with other fans informal and professional.

I think this is going to have fun, and I'm hoping my readers will have just as much fun.